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| author | Mike Rapoport (Microsoft) <rppt@kernel.org> | 2026-05-13 11:14:16 +0300 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2026-07-04 13:44:17 +0200 |
| commit | ec1c9e8962555b1766d059dc02760645c2ff62ff (patch) | |
| tree | 2db3525c165ab6746ab995aca3fa1b4b36d88816 | |
| parent | 7216ce8cb12fee44e309503955bb83806b106129 (diff) | |
| download | linux-stable-ec1c9e8962555b1766d059dc02760645c2ff62ff.tar.gz linux-stable-ec1c9e8962555b1766d059dc02760645c2ff62ff.zip | |
userfaultfd: ensure mremap_userfaultfd_fail() releases mmap_changing
commit 0496a59745b0723ea74274db16fd5c8b1379b9a9 upstream.
Sashiko says:
mremap_userfaultfd_prep() increments ctx->mmap_changing to stall
concurrent operations, but mremap_userfaultfd_fail() does not
decrement it before dropping the context reference.
If an mremap operation fails, ctx->mmap_changing remains elevated. This
will causes subsequent userfaultfd operations like a UFFDIO_COPY to fail
with -EAGAIN.
Decrement ctx->mmap_changing in mremap_userfaultfd_fail().
Link: https://sashiko.dev/#/patchset/20260430113512.115938-1-rppt@kernel.org
Link: https://lore.kernel.org/20260513081416.495963-1-rppt@kernel.org
Fixes: df2cc96e7701 ("userfaultfd: prevent non-cooperative events vs mcopy_atomic races")
Signed-off-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Reviewed-by: David Hildenbrand (Arm) <david@kernel.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Jan Kara <jack@suse.cz>
Cc: Peter Xu <peterx@redhat.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| -rw-r--r-- | fs/userfaultfd.c | 2 |
1 files changed, 2 insertions, 0 deletions
diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c index df18fb453403..a67afdbbf77a 100644 --- a/fs/userfaultfd.c +++ b/fs/userfaultfd.c @@ -767,6 +767,8 @@ void mremap_userfaultfd_fail(struct vm_userfaultfd_ctx *vm_ctx) if (!ctx) return; + atomic_dec(&ctx->mmap_changing); + VM_WARN_ON_ONCE(atomic_read(&ctx->mmap_changing) < 0); userfaultfd_ctx_put(ctx); } |